Joseon and Ming drive the Mongolians and Manchus to Eastern Siberia and Alaska, What would be the consequences to the Native Americans and Eastern Siberians..
That depends on definition. Ive seen atlases who tripart Siberia into the West Siberia plain (the river lowlands of Ob and contributaries), the Central Siberian Plateau (mountainous area east of the RIver Yenisey) and East Siberia. Where East Siberia would very much be the part north of China.Firstly, Siberia is actually the region directly north of the 'stans and starts at the Urals, not the Pacific coast of modern Russia.
but on the actual topicSo if for some reason the Chinese and Koreans began pushing northwards, they'd likely assimilate or exterminate the preexisting peoples, not chase them away (unless they migrated west, as the Huns did in the first few centuries CE).